Liquid measuring and dispensing pump



Nov; 25,1952 o. MAISCH 2,619,040

- LIQUID MEASURING AND DISPENSING PUMP Filed March 15, 1949 J j J Zextends radially from the shaft into a groove in the gear; the grooverunning parallel to the axis of the gear. Consequently, the gears arefloating in the sense that they can find their own seats on thesurrounding casing, without being constrained against doing so by theirsupporting shafts.

In the pump disclosed in my said prior application the pump gears andthe walls between which they lie are composed of stainless steel, sothat considerable clearance is required to allow the gears to revolvefreely. I have found that if at least one of each pair of surfaces onthe ears and the casing, that touch each other when there is anunusually close fit between the gears and the casing, is composed of aself lubricating bearing material, the fit may be sufliciently close toinsure great accuracy in the amount of liquid pumped without interferingwith the free rotation of the gears at all speeds. This holds true eventhough the gears or the casing, or both, be composed of somenon-metallic material. For most purposes, carbon bearing materials ofthe harder types now in use are satisfactory. However, when certainacids are to be handled some of the plastic compounds, particularly oneknown as Teflon, which is a polytetrafluoroethylenepolymer serve mypurpose better than does carbon; as this compound will withstand boilingin aqua regia, hydrofluoric acid or fuming nitric acid without change inweight or properties. Nylon may also be used in some instances whereTeflon would serve.

There are of course many ways in which a pump may be constructed tosecure the advantages of my invention. In the drawing I have illustrateda simple arrangement in which metal and carbon are combined in a mannerto create a strong, durable structure at a reasonably low cost. In thisparticular embodiment, as in my aforesaid application, the casing 2 is acup shaped metal member, while the foundation of end wall 5 is a thickmetal plate. The partition wall 8 takes the form of a thick disc ofcarbon set against the inner face of end wall 6 and recessed to formpump chamber 9 with its central wings 9. End wall 6, also, is recessedon its inner side, as at 6 and thick discs 2| and 22, a little larger indiameter than the pump gears, are set into this recess and leave theresultant inner face of the Wall flat. When Walls 6 and 8 are placedagainst each other, the carbon discs 2| and 22 form a cover for the pumpchamber, as well as bearings for one end of each of the shafts l3 and il.

The speed reducing gearing is substantially the same as in my prior pumpexcept that none of the driving gears or pinions is on shaft section It.The motor shaft 24 has fixed thereon a pinion 25 that meshes with alarge gear wheel 26 mounted on end wall I. Rotatable with gear 26 is asecond pinion 21 that meshes with a large gear wheel 28 that is loose onthe motor shaft but is held against movement lengthwise of the shaft.Shaft section I5 has a thick collar 29 fixed on its end close to the endof the motor shaft. Gear wheel 28 has thereon a pair of pins 30 thatextend toward collar 29; whereas the collar is provided with lugs 3|that are engaged by the pins which thus serve to turn shaft section l5whenever the motor shaft turns. Therefore shaft M, with its extensionI5, is of the floating type, carrying none of the driving wheels andbeing subjected only to balanced turning forces that do not restrain itagainst lengthwise movement.

Loose on shaft section I5 is a deep cup-shaped element 32 whose flatbottom bears against wall 8.

Within the cup is an 0 ring sealing element 33 fitting on the shaft.Also in the cup, outwardly from the sealing element, is a washer 34, andbetween the washer and the collar, around the shaft, is a compressionspring 35. Members 29 and 32 are loosely coupled together by means ofpins 36 on member 29 extending into notches 31 in the rim of the cup.With this arrangement, the shaft l4, with its extension l5 and all partson the latter turn as a single unit, wall 8 is yieldingly clampedbetween shoulder M on shaft l4 and the flat bottom of cup 32. Therefore,because the pump gear I2 is not fixed to shaft M and that shaft is notrestrained by the driving means therefor, a very effective seal againstleakage from the pump chamber along shaft section I5 is provided.

It will be seen that, with the gears rotating in the direction of thearrows in Figs. 3 and 4, liquid is carried upwardly and toward the rightby gear I and downwardly and toward the right by gear I2, from the lefthand end of the central portion of the pump chamber and is dischargedinto the right hand or outlet end of the chamber. Since the outlet endof the chamber is full of liquid while the pump is running, some of theliquid is carried back again from there toward the inlet side or end,between the intermeshing teeth. When the gear teeth are so shaped thatthere is no backlash, this liquid is trapped in pockets formed betweenthem, these pockets diminishing in size as they traverse the distancefrom the outlet compartment of the chamber to the inlet compartment;and, the liquid being incompressible, it causes trouble unless means forescape are provided.

In order to permit the trapped liquid to escape from the pockets betweenintermeshing teeth, I have out into the inner faces of Walls 6 and 8little recesses 38 and 39, respectively, a little to the outlet side ofthe plane containing the axes of the gears and midway between such axes.The recesses, which need not be deep, may be round and of a diameterlarge enough to permit the pocket A in Fig. 4 to remain in communicationtherewith until the tooth that is partially entered into the pocketmoves down and fllls the latter.

By providing suitable motor controlling means, the pump may be caused torun very slowly, very rapidly, or at any intermediate speed for anypredetermined periods of time; thereby making it possible to deliver anydesired accurately measured quantity of liquid, or a liquid flow at anydesired, accurately measured rate for any desired length of time.

Iclaim:

In combination, a pump casing, intermeshing pump gears in the casing, ashaft for one of said gears interlocked therewith to compel the gears toturn in unison and be relatively movable axially of the shaft, saidshaft having a shoulder bearing against the inner side of the casingwall and an extension passing outwardly through such wall, means.mounted on said extension yieldingly to hold said shoulder against saidwall, a motor-driven speed-reducing means terminating in a rotatablepart coaxial with the shaft and adjacent to the outer end of the latter,and an interlock between said shaft and said rotatable part which allowsthem free relative axial movements while compelling rotary movements inunison with each other.

OLIVER MAISCH.

(References on following page) REFERENCES CITED The following referencesare of record in th file of this patent:

UNITED STATES PATENTS Number Name Date Radu Jan. 28, 1908 McIntyre Dec.16, 1930 Whaley Dec. 1, 1931 Hofmann Apr. 19, 1932 Bochmann et a1 Aug.4, 1936 Hansen Oct. 19, 1937 Johnson June 4, 1940 Thomson July 1, 1941Number Number 0 National Carbon M-8000-A, Oct. 1944.

National Carbon 6 Name Date Funk Apr. 7, 1942 Rea Dec. 7, 1943 FOREIGNPATENTS Country Date Great Britain June 6, 1929 OTHER REFERENCES CompanyInc., Catalogue Company Inc., Catalogue M-9100-A, Jan. 1947.

